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Clarification of postmortem metabolite changes can help characterize the process of biological degradation and facilitate investigations of forensic casework, especially in the estimation of postmortem interval (PMI). Metabolomics can provide information on the molecular profiles of tissues, which can aid in investigating postmortem metabolite changes. In this study, liquid chromatography-mass spectrometric (LC-MS) analysis was performed to identify the metabolic profiles of rat femoral muscle at ten periods of time after death within 168 h. The results obtained by reversed-phase liquid chromatography (RPLC)- and hydrophilic interaction liquid chromatography (HILIC)- electrospray ionization (ESI±) have revealed more than 16,000 features from all four datasets. Furthermore, 915 of these features were identified using an in-house database. Principal component analysis (PCA) demonstrated the time-specific features of molecular profiling at each period of time after death. Moreover, results from partial least squares projection to latent structures-discriminant analysis (PLS-DA) disclosed a strong association of metabolic alterations of at least 59 metabolites with the time since death, especially within 48 h after death, which expounds these metabolites as potential indicators in PMI estimation. Altogether, our results illustrate the potentiality of metabolic profiling in the evaluation of PMI and provide candidate metabolite markers with strong correlation with time since death for forensic purpose. [ABSTRACT FROM AUTHOR]

Quince (Cydonia oblonga) leaves are traditionally reported to alleviate the risk of cardiovascular disease. The study envisaged to explore the in vitro and in vivo phytochemical and cardio protective potential of quince extract respectively. Different solvent extracts (Aqueous, Ethanolic, Hydroethanolic, Methanolic) of quince leaf obtained via two different extraction methods (Ultrasonication and Reflux) were evaluated for the phytochemical and antioxidant analysis. Among all the extracts, quince ethanolic extract, extracted via sonication was found to have the maximum phenolics (39.89 ± 0.67 mg GAE/g DW), flavonoids (21.51 ± 1.0 mgRE/g DW) and an anti-oxidant potential 2,2-diphenyl-1-picryl-hydrazyl radical (DPPH) with IC 50 value of 168.88 ± 2.24 μg/ml. The High-performance thin layer chromatograph (HPTLC) and ultrahigh performance liquid chromatography mass spectrometry (UPLC-MS) analysis confirmed the presence of bio active compounds. Furthermore, the in vivo activity was ascertained against Doxorubicin (DOX) induced cardio toxicity in rats fed orally with the extract at 160 and 320 mg/kg body weight. The pre-treated groups significantly assuaged the changes induced by DOX in the electrocardiogram (ECG). Additionally, it mitigated the elevation in the blood serum parameters; aspartate transaminase (AST), lactate dehydrogenase (LDH), creatinine kinase-MB (CK- MB) and also repressed glutathione (GSH) depletion and rise in malondialdehyde (MDA) level induced by DOX. Furthermore, improvement in histopathological changes of the heart tissue concomitant to DOX induced toxicity was also observed such as, reduced degeneration, necrosis, inflammation and apoptosis. Thus, it could be concluded that cardioprotective activity of quince extract accredited to the occurrence of phytoconstituents prevented the DOX induced cardiotoxicity and helped to reinstate the cardiac damage in rats. [Display omitted] [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to develop a LC-MS method to determine amiodarone (AMI) and its major metabolite desethylamiodarone (DEA) from rat plasma released from the adipose tissue of AMI treated rats subjected to a weight gain/weight loss cycle. Methods: Separation of the compounds was performed on a Kinetex 2.6 µm C18 100 x 4.6 mm column under isocratic conditions using a mixture of acetonitrile: 0.1% formic acid 65:35 at a flow rate of 0.5 ml/min. Detection of the analyte was performed by electrospray positive ionization, the monitored ions being 135 m/z from 646 for AMI and 135 m/z of 618 for DEA. Analytes were extracted after plasma protein precipitation with methanol. Results: The developed method presented specificity and linearity on the concentration range of 25-2500 ng/ml plasma for AMI and 2.5-1250 ng/ml plasma for DEA and the precision and accuracy of the method at all of quality control concentration levels including LLOQ were according to official guidelines for validating analytical methods. Conclusions: A sensitive and accurate LC-MS method has been developed with a much lower LLOQ than literature data to detect the plasma concentration differences of the studied analytes that result from forced lipolysis and mobilization from the adipose tissue. [ABSTRACT FROM AUTHOR]

Abstract: To rapidly identify and classify complicated components and metabolites for traditional Chinese medicines, a liquid chromatography with quadrupole time‐of‐flight mass spectrometry method combined with multiple data‐processing approaches was established. In this process, Kai‐Xin‐San, a widely used classic traditional Chinese medicine preparation, was chosen as a model prescription. Initially, the fragmentation patterns, diagnostic product ions and neutral loss of each category of compounds were summarized by collision‐induced dissociation analysis of representative standards. In vitro, the multiple product ions filtering technique was utilized to identify the chemical constituents for globally covering trace components. With this strategy, 108 constituents were identified, and compounds database was successfully established. In vivo, the prototype compounds were extracted based on the established database, and the neutral loss filtering technique combined with the drug metabolism reaction rules was employed to identify metabolites. Overall, 69 constituents including prototype and metabolites were characterized in rat plasma and nine constituents were firstly characterized in rat brain, which may be the potential active constituents resulting in curative effects by synergistic interaction. In conclusion, this study provides a generally applicable strategy to global metabolite identification for the complicated components in complex matrix and a chemical basis for further pharmacological research of Kai‐Xin‐San. [ABSTRACT FROM AUTHOR]

Capillary scale (100 mm × 150 μm id) UPLC/MS/MS, performed using reversed-phase gradient chromatography on sub 2 μm particles, has been successfully employed for the characterization of the metabolites of the drug tienilic acid (TA) excreted via the urine following oral administration to the rat. The capillary LC system provided a significant increase (range ca. 11–33-fold) in sensitivity compared with a conventional 150 mm × 2.1 mm id UPLC system. An investigation of the effect of the injection volume and sample mass loading on the capillary column on the results obtained for both endogenous metabolites and TA was performed. This demonstrated that the injection of up to 2 μL of rat urine onto the system was permitted whilst still providing excellent chromatographic results and robustness. Qualitative analysis of the urine revealed the presence of TA itself and a total of 15 metabolites of the drug, including those resulting from biotransformations such as hydroxylation or conjugation. The capillary chromatography system was shown to be robust, and capable of providing comprehensive drug metabolite profiles from small format urine samples such as those obtained from preclinical studies in rodents. [ABSTRACT FROM AUTHOR]

A sensitive, selective, and reliable LC-MS/MS method was developed and validated for simultaneous quantification of venlafaxine (VEN) and its 5 metabolites (ODV, NDV, NNDDV, OHV and NODDV) in rat plasma. The calibration ranges are 15.0 to 6000 ng/mL for VEN, 1.00 to 400 ng/mL for ODV, 5.00 to 2000 ng/mL for NDV, 1.00 to 400 ng/mL for NNDDV, 10.0 to 4000 ng/mL for OHV, and 0.200 to 20.0 ng/mL for NODDV. Briefly, 50 μL of rat plasma was extracted using liquid-liquid extraction (LLE) with methyl tert -butyl ether (MTBE). The analytes were separated on an Agilent SB-Phenyl (50 mm × 4.6 mm, 3.5 μm) column using a binary gradient of 0.1% formic acid in water versus 0.1% formic acid in acetonitrile at a flow rate of 0.8 mL/min. The method was validated following FDA guidance for bioanalytical method validation. Validated method was successfully applied to a pharmacokinetic study of VEN orally administered to rats. [ABSTRACT FROM AUTHOR]

Arecoline is the primary active and toxic constituent of areca nut. Arecaidine and arecoline N -oxide are two major active metabolites of arecoline. In this work, an accurate and simple high performance liquid chromatography tandem mass spectrometry method for simultaneous quantification of arecoline, arecaidine and arecoline N -oxide in rat plasma was developed and fully validated to study their pharmacokinetic behaviors in rats. After extracted from rat plasma by protein precipitation with methanol and then concentrated, the analytes were chromatographic separated on a Sepax Sapphire C 18 analytical column. The mobile phase consisted of methanol and 2 mM ammonium acetate buffer solution containing 0.2% ( v/v ) formic acid (8:92, v/v ) under isocratic elution. The analytes were detected by multiple reaction monitoring (MRM) with an electrospray ionization source in the positive ion mode. The transitions of m / z 156.2 → 53.2,  m / z 142.2 → 44.2 and m / z 172.2 → 60.2 were selected for arecoline, arecaidine and arecoline N -oxide, respectively. The method was linear over the concentration range of 0.5–100 ng/mL for arecoline, 5–5000 ng/mL for arecaidine and arecoline N -oxide with no carry-over effect. The accuracies and intra- and inter-batch precisions were all within the acceptance limits. No matrix effect and potential interconversion between the analytes and other metabolites were observed in this method. The validated method was further employed to a preclinical pharmacokinetic study of arecoline, arecaidine and arecoline N -oxide after oral treatment with 20 mg/kg arecoline to rats. [ABSTRACT FROM AUTHOR]

QO-58 lysine (QO-58L) as a new potassium channel opener, reported to have a potential activity to cure neuropathic pain. The aim of this research is to develop and validate a high-performance liquid chromatography with tandem spectrometry (LC-MS/MS) method for the quantification of QO-58L in rat urine, feces and bile. In addition, analyze and identify the metabolites in urine and bile. The assay for this compound in samples detected with multiple reaction monitoring mode (MRM), and take nimodipine as internal standards (IS). To better understand the biotransformation of QO-58L, metabolites in urine and bile were identified by using ultra high performance liquid chromatography tandem quadrupole/time of flight mass spectrometry (UHPLC-Q-TOF-MS) in the positive and negative ion mode. Urine, feces and bile were quantified by three new methods. The results showed that: QO-58L was mainly eliminated through fecal route (92.94%), a small amount of it via biliary excretion (2.05%), and rarely through urinary excretion (0.024%). As a result, there are 11 metabolites were identified, including 8 phase I metabolites resulting from elimination, hydroxylation and dihydroxylation, and 3 phase II metabolites originating from sulfation, N -acetylcysteine conjugation and glucuronidation. Furthermore, the newly discoveries of excretion and metabolism significantly expanded our understanding and was going to be greatly helpful for QO-58L's further pharmacokinetic study in vivo. [ABSTRACT FROM AUTHOR]

Background: This study aims at characterizing the in vitro metabolism of cryptolepine using human and rat hepatocytes, identifying metabolites in rat plasma and urine after a single cryptolepine dose, and evaluating the single-dose oral and intravenous pharmacokinetics of cryptolepine in male Sprague Dawley (SD) rats. Methods: The in vitro metabolic profiles of cryptolepine were determined by LC-MS/MS following incubation with rat and human hepatocytes. The in vivo metabolic profile of cryptolepine was determined in plasma and urine samples from Sprague Dawley rats following single-dose oral administration of cryptolepine. Pharmacokinetic parameters of cryptolepine were determined in plasma and urine from Sprague Dawley rats after single-dose intravenous and oral administration. Results: Nine metabolites were identified in human and rat hepatocytes, resulting from metabolic pathways involving oxidation (M2-M9) and glucuronidation (M1, M2, M4, M8, M9). All human metabolites were found in rat hepatocyte incubations except glucuronide M1. Several metabolites (M2, M6, M9) were also identified in the urine and plasma of rats following oral administration of cryptolepine. Unchanged cryptolepine detected in urine was negligible. The Pharmacokinetic profile of cryptolepine showed a very high plasma clearance and volume of distribution (Vss) resulting in a moderate average plasma half-life of 4.5 h. Oral absorption was fast and plasma exposure and oral bioavailability were low. Conclusions: Cryptolepine metabolism is similar in rat and human in vitro with the exception of direct glucuronidation in human. Clearance in rat and human is likely to include a significant metabolic contribution, with proposed primary human metabolism pathways hydroxylation, dihydrodiol formation and glucuronidation. Cryptolepine showed extensive distribution with a moderate half-life. [ABSTRACT FROM AUTHOR]

We present a validated liquid chromatography with tandem mass spectrometry method for simultaneous determination of 20-( S)-protopanaxatriol and its two oxidative stereoisomeric metabolites (20 S,24 S)-epoxy-dammarane-3,6,12,25-tetraol (M1) and (20 S,24 R)-epoxy-dammarane-3,6,12,25-tetraol (M2) in rat plasma. 20-( S)-Protopanaxatriol, M1, and M2 were extracted with methanol and separated on an ACQUITY HSS T3 column. The mass spectrometry detection was accomplished in selected reaction monitoring mode with precursor-to-product ion transitions of m/z 493.4→143.1 for M1 and M2, m/z 475.4→391.3 for 20-( S)-protopanaxatriol, and m/z 459.4→375.3 for 20-( S)-protopanaxadiol (internal standard). The method showed good linearity over the concentration ranges of 1-1000 ng/mL for 20-( S)-protopanaxatriol and 0.5-200 ng/mL for M1 and M2, with correlation coefficients of more than 0.995. The lower limits of quantification for 20-( S)-protopanaxatriol, M1, and M2 were 1, 0.5, 0.5 ng/mL, respectively. The intra- and interday precisions (RSD, %) were less than 10.41% while the accuracy (relative error, %) ranged from -3.14 to 8.73%. Under the current conditions, M1 and M2 were completely separated within 3 min. The validated assay was successfully applied to evaluating pharmacokinetic profiles of 20-( S)-protopanaxatriol, M1, and M2 in rat. [ABSTRACT FROM AUTHOR]

Orientin and vitexin, 4’-hydroxyl-2-phenylchromen-4-one, are both major flavones derivatives found in Trollius ledebourii possessing definite pharmacological activities. In this study, in vitro metabolisms investigated on rat liver microsomes (RLMs) and in vivo metabolisms explored on Male Sprague Dawley rats of orientin and vitexin were tested, respectively. A systematic method based on ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) was developed to characterize metabolites by means of electrospray ionization (ESI) mass spectrometry in positive ion mode. An on-line data acquisition method multiple mass defect filter (MMDF) combined with dynamic background subtraction (DBS) was developed to observe probable relevant metabolites. By comparison of chromatographic behaviors with reference substances, exact protonated ions, MS/MS fragment ions and relevant literature, a total of 12 metabolites of orientin and 23 metabolites of vitexin were detected, respectively, which suggested that orientin is more metabolically stable than vitexin. Oxidation, methylation, acetylation, reduction, loss of C 6 H 10 O 5 and glucuronide conjugation were the major biotransformation routes of both of them in rats. More significant, glutamine conjugation, loss of CO and loss of CH 2 O were the unique metabolic pathways of vitexin compared with that of orientin for the first time. Besides, most metabolites were observed in rat urine and feces, implying that urine and feces were the active metabolic places for flavones. This is the first study on metabolisms of orientin and vitexin in vitro and in vivo simultaneously and the proposed metabolic pathways of them might provide further understanding of their pharmacological mechanisms and later study on their excretion. [ABSTRACT FROM AUTHOR]

Gentiopicroside is a natural secoiridoid glycoside that may require metabolic activation to exert pharmacological effects. In this study, two active metabolites of gentiopicroside (M1 and M2) were isolated from rat urines and identified with our previous method. Most importantly, a fast, sensitive and selective ultra high-performance liquid chromatography–tandem mass spectrometry method was developed to simultaneously determine gentiopicroside and its two metabolites in rat plasma. The analytes and internal standard (swertiamarin) were separated on an ACQUITY UPLC ® BEH C18 column (2.1 × 50 mm, 1.7 μm) using gradient elution by acetonitrile and 0.1% formic acid at a flow rate of 0.4 mL/min. The mass spectrometry detector was operated in the multiple reaction monitoring with positive ionization mode. The method had a good linearity over the concentration range of 0.2–10,000 ng/mL for gentiopicroside and 0.1–5000 ng/mL for the two metabolites. The validated method was successfully applied to the pharmacokinetic study of gentiopicroside and its metabolites after single oral administration of gentiopicroside (150 mg/kg) to rats (n = 8). The pharmacokinetic differences between gentiopicroside and its two metabolites were identified.Results provided the evidence for in vivo metabolism-based activation of gentiopicroside. [ABSTRACT FROM AUTHOR]

Genipin-1- o -glucuronic acid and genipin-monosulfate are two major metabolites from geniposide and genipin. Based on diabetic rat model, we developed a simultaneous quantification method to investigate their comparative pharmacokinetics by online mircrodialysis-ultra performance liquid chromatography–mass spectrometry (MD-UPLC–MS/MS) without their standard compounds. Online microdialysis sampling could avoid unexpected contamination or degradation of the analytes during the storage and transfer steps. Combined with good sensitivity, selectivity and selectivity of UPLC–MS/MS, online MD-UPLC–MS/MS method could real-timely monitor metabolites in rat blood for quantitative analysis. Our research found that AUC 0→t of genipin-1- o -glucuronic acid and genipin-monosulfate in blood of diabetic group were 17.68 and 7.58 times than those in normal group, respectively, and AUC 0→t of genipin-1- o -glucuronic acid was 2.28 times than that of genipin-monosulfate in blood of diabetic group, which revealed the effect of diabetes on the pharmacokinetic properties of the two metabolites. This study not only provides an approach for pharmacokinetic studies for various metabolites from herb medicines, but also can predict druggability of their bioactive metabolites. The insight obtained should facilitate drug development and toxicity research. [ABSTRACT FROM AUTHOR]

It has been proved that the purine metabolic pathway has been implicated in various biological disorders including gout, diabetes, coronary heart diseases, and neurodegenerative diseases. The analysis of the purine metabolic pathway in organisms reveals important alterations under different physiological and pathological conditions, which contributes to the pathological study, diagnosis, and therapy of related diseases. In the present study, an ultra-high performance liquid chromatography with ultraviolet and tandem mass spectrometry (UHPLC-UV–MS/MS) method was developed for conducting the comprehensive analysis of the metabolite profiles of the purine pathway in rat plasma through a single analysis. The purine metabolites including adenosine-5′-monophosphate, guanosine-5′-monophosphate, adenosine, inosine, guanosine, inosine-5′-monophosphate, deoxyadenosine, deoxyguanosine, deoxyinosine, xanthine, hypoxanthine, and uric acid, were separated and quantified in the short running time of 10 min. After rapid chromatographic separation achieved by an Agilent Zorbax SB-Aq column, high concentration of uric acid and the remaining purine metabolites at lower levels were respectively detected by ultraviolet detector and triple quadruple mass spectrometry within a single analysis. The proposed method was validated by applying charcoal-stripped plasma as a matrix and it was proved to be linear ( R 2 > 0.982), accurate (with a relative error for accuracy < ± 15% and the relative standard deviation for intra- and inter-run precision <11%) and reproducible (with a matrix effect ranging between 86.49% and 111.44% with a maximum RSD of 8.69%). As a result, the method was successfully applied to the quantification of the endogenous purine metabolites in rat plasma. It was found that the concentration levels of the purine metabolites may keep a physiological balance as an integrated system in normal individuals and the concentration level of uric acid in rat plasma was 64 μM which was more than 200 times greater than the other purine metabolites. The established method and the measurement of the concentration of these purines in normal rat plasma may help the investigation of the action mechanisms between purine disorders and related diseases. [ABSTRACT FROM AUTHOR]

AM-2201 is a popular synthetic cannabinoid first synthesized in 2000. AM-2201 pharmacokinetic and pharmacodynamic data are scarce, requiring further investigation. We developed a sensitive method for quantifying AM-2201 and 13 metabolites in plasma to provide a tool to further metabolic, pharmacokinetic and pharmacodynamic studies. Analysis was performed by liquid chromatography-tandem mass spectrometry. Chromatographic separation was performed by gradient elution on a biphenyl column with 0.1% formic acid in water/0.1% formic acid in acetonitrile:methanol 50:50 ( v/v ) mobile phase. Sample preparation (75 μL) consisted of an enzymatic hydrolysis and a supported liquid extraction. The method was validated with human plasma with a 0.025 or 0.050–50 μg/L working range, and cross-validated for rat plasma. Analytical recovery was 88.8–110.1% of target concentration, and intra- (n = 30) and inter-day (n = 30) imprecision < 11.9% coefficient of variation. Method recoveries and matrix effects ranged from 58.4–84.4% and −62.1 to −15.6%, respectively. AM-2201 and metabolites were stable (±20%) at room temperature for 24 h, at 4 °C for 72 h, and after three freeze-thaw cycles, and for 72 h in the autosampler after extraction. The method was developed for pharmacodynamic and pharmacokinetic studies with controlled administration in rats but is applicable for pre-clinical and clinical research and forensic investigations. Rat plasma specimen analysis following subcutaneous AM-2201 administration demonstrated the suitability of the method. AM-2201, JWH-018 N -(5-hydroxypentyl), and JWH-018 N -pentanoic acid concentrations were 4.8 ± 1.0, 0.15 ± 0.03, and 0.34 ± 0.07 μg/L, respectively, 8 h after AM-2201 administration at 0.3 mg/kg (n = 5). [ABSTRACT FROM AUTHOR]

In this study, we developed and validated a new, rapid, specific and sensitive ultra-performance liquid chromatography–tandem mass spectrometric (UPLC–MS/MS) method to simultaneously determine parecoxib sodium (PX) and its active metabolite, valdecoxib (VX), in rat plasma. Plasma samples were prepared by plasma protein precipitation combined with a liquid-liquid extraction method. The separation was carried out on a Kinetex C 18 column (2.1 mm × 50 mm, 2.6 μm) with a gradient elution using methanol (A) and a 2 mM ammonium acetate aqueous solution (B). The analysis was performed in less than 3 min with a flow rate of 0.2 mL/min. Ketoprofen was used as an internal standard (IS). Mass spectrometric detection was conducted with a triple quadrupole detector equipped with electrospray ionization in the negative ion mode (ESI − ) using multiple reaction monitoring (MRM). The calibration curves were linear over the concentration ranges of 5–4000 ng/mL for PX and 5–2000 ng/mL for VX with all correlation coefficients greater than 0.998. The intra- and inter-day relative standard deviations (RSD) for both analytes were within 15% and the accuracy was within 85–115% at all quality control levels. The mean extraction recoveries for all analytes obtained from three concentrations of QC plasma samples were more than 89.0% efficient. Selectivity, matrix effect, dilution integrity and stability were also validated. The method was successfully used to investigate the pharmacokinetics of PX and VX in rat plasma after intravenous and intramuscular administration of PX. [ABSTRACT FROM AUTHOR]

Isocorynoxeine (ICOR) is one of the bioactive oxindole alkaloids inUncariaspecies. This study presents the pharmacokinetics and mass balance of ICOR in rats after oral dose of 40.0 mg/kg and intravenous dose of 4.0 mg/kg through detection of ICOR and its in vivo metabolites, using an optimized LC-MS with recoveries ranged from 94 to 104%, accuracy varied from 96 to 103%, and relative standard deviation for assay being less than 5%. ICOR reached its Cmaxof 336.7 ng/mL in plasma 3 hr after oral dose. The phase I metabolites of ICOR, 11-hydroxyisocorynoxeine (M1), and 10-hydroxyisocorynoxeine (M2) were detected in rat heart, kidneys, urine, and feces; whereas, in rat liver and bile, M1, M2, along with phase II metabolites, 11-hydroxyisocorynoxeine 11-O-β-D-glucuronide, and 10-hydroxyisocorynoxeine 10-O-β-D-glucuronide were identified. ICOR (77.0%) was excreted into feces and urine after oral administration within 72 hr, 0.93% drained into bile in 8 hr, 17.9% biotransformed into M1 and M2 at a ratio ofca. 1:1, and 0.028% detected in main organs attmax, in which brain uptake index is 3.2 ng/g. This work affords a developed and validated LC-MS for simultaneous determination of ICOR and itsin vivometabolites with improved precision and accuracy. [ABSTRACT FROM PUBLISHER]

To establish a rapid and sensitive ultra performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) method for the determination of concentration of nintedanib and its metabolite BIBF 1202 in rat plasma. The nintedanib and its metabolite and the internal standard (diazepam) were separated on an Acquity UPLC BEH C18 chromatography column (2.1 mm × 50 mm, 1.7 μm) using gradient elution with a mobile phase of acetonitrile and 0.1% formic acid in water at a flow rate of 0.30 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m / z 540.3 → 113.1 for nintedanib, m / z 526.3 → 113.0 for BIBF 1202 and m / z 285.3 → 193.1 for diazepam (IS) using a positive electrospray ionization interface. The method was validated for 1.0–200 ng/mL for nintedanib and 0.5–100 ng/mL for BIBF 1202 using 100 μL of plasma sample. Total time for each chromatograph was 3.0 min. The intra- and inter-day precision and accuracy of the quality control samples at low, medium, and high concentration levels exhibited relative standard deviations (RSD) <10.8% and the accuracy values ranged from −11.9% to 10.4%. The method was successfully applied to a pharmacokinetic study of nintedanib and BIBF 1202 in rats after oral administration of nintedanib. [ABSTRACT FROM AUTHOR]

In this work, a rapid and sensitive ultra performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) method for the determination of ledipasvir, sofosbuvir and its metabolite GS-331007 in rat plasma was developed. The analytes and the internal standard (diazepam) were separated on an Acquity UPLC BEH C18 chromatography column (2.1 mm × 50 mm, 1.7 μm) using gradient elution with a mobile phase of acetonitrile and 0.1% formic acid in water at a flow rate of 0.4 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m/z 889.8 → 130.1 for ledipasvir, m/z 530.3 → 243.1 for sofosbuvir, m/z 261.5 → 113.1 for GS-331007 and m/z 285.2 → 193.1 for diazepam (IS) using a positive electrospray ionization interface. The method was validated over a concentration range of 2–500 ng/mL for ledipasvir, 10-2000 ng/mL for sofosbuvir and 10-2000 ng/mL for GS-331007. Total time for each chromatography was 3.0 min. The intra- and inter-day precision and accuracy of the quality control samples at low, medium, and high concentration levels exhibited relative standard deviations (RSD) < 10.2% and the accuracy values ranged from −9.8% to 11.2%. The method was successfully applied to a pharmacokinetic study of ledipasvir, sofosbuvir and GS-331007 in rats. [ABSTRACT FROM AUTHOR]

A simple, rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed and validated for the simultaneous quantitation of metformin (MTF), metoprolol (MET), α-hydroxymetoprolol (HMT) and O-desmethylmetoprolol (DMT) in rat plasma using paracetamol as an internal standard (IS), respectively. The sample preparation involved a proteinprecipitation method with methanol after the addition of IS. The separation was performed on an Agilent HC-C18 column (4.6 × 250 mm, 5 μm) at a flowrate of 1.0 mL/min, using methanol-water containing 0.1% formic acid (39:61, v/v) as mobile phase, and total run time was 8.5 min. MS-MS detection was accomplished in multiple reaction monitoring mode with positive electrospray ionization. The monitored transitions were m/z 130.1→60.2 for MTF, m/z 268.2→116.1 for MET, m/z 284.2→ 116.1 for HMT, m/z 254.2→116.1 for DMT and m/z 152.3→110.1 for IS. The method was fully validated in terms of selectivity, linearity, accuracy, precision, stability, matrix effect and recovery over a concentration range of 19.53-40,000 ng/mL for MTF, 3.42-7,000 ng/mL for MET, 2.05-4,200 ng/mL for HMT and 1.95-4,000 ng/mL for DMT, respectively. The analytical method was successfully applied to drug interaction study of MTF and MET after oral administration of MTF and MET. Results suggested that the coadministration of MTF and MET results in a significant drug interaction in rat. [ABSTRACT FROM AUTHOR]

This study describes the development of a simple LC-ESI–MS/MS method with polarity switching for the simultaneous analysis of phenoxyethanol (PE) and its major metabolite, phenoxyacetic acid (PAA), in rat plasma, urine, and 7 different tissues. The assay was validated to demonstrate the linearity, precision, accuracy, LLOQ, recovery, and stability by using the matrix matched QC samples. The assay achieved the LLOQ of 10 and 20 ng/mL of PE and PAA, respectively, for plasma samples and the LLOQ of 20 and 50 ng/mL of PE and PAA, respectively, for urine and tissue samples. This method was successfully applied to the percutaneous absorption, distribution, metabolism, and excretion studies in rats. The absolute topical bioavailability of PE was 75.4% and 76.0% for emulsion and lotion, respectively. Conversion of PE to PAA was extensive, with the average AUC PAA -to- AUC PE ratio being 4.4 and 5.3 for emulsion and lotion, respectively. The steady-state tissue-to-plasma PE concentration ratio ( K p ) was higher than unity for kidney, spleen, heart, brain, and testis and was lower ( ≤ 0.6) for lung and liver, while the metabolite K p ratio was higher than unity for kidney, liver, lung, and testis and was lower ( ≤ 0.3) for other tissues. Findings of this study may be useful to evaluate the relationship between exposure and toxic potential of PE in risk assessment. [ABSTRACT FROM AUTHOR]

Tinoridine is a nonsteroidal anti-inflammatory drug and also has potent radical scavenger and antiperoxidative activity. However, metabolism of tinoridine has not been thoroughly investigated. To identify in vivo metabolites, the drug was administered to Sprague-Dawley rats (n = 5) at a dose of 20mgkg-1, and blood, urine and feces were collected at different time points up to 24 h. In vitro metabolism was delved by incubating the drug with rat liver microsomes and human liver microsomes. The metabolites were enriched by optimized sample preparation involving protein precipitation using acetonitrile, followed by solid-phase extraction. Data processes were carried out usingmultiplemass defects filters to eliminate false-positive ions. A total of 11metabolites have been identified in urine samples including hydroxyl, dealkylated, acetylated and glucuronide metabolites; among them, some were also observed in plasma and feces samples. Only two major metabolites were formed using liver microsomal incubations. These metabolites were also observed in vivo. All the 11 metabolites, which are hitherto unknown and novel, were characterized by using ultrahigh-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry in combination with accurate mass measurements. Finally, in silico toxicological screening of all metabolites was evaluated, and two metabolites were proposed to show a certain degree of lung or liver toxicity. [ABSTRACT FROM AUTHOR]

The metabo-ring initiative brought together five nuclear magnetic resonance instruments (NMR) and 11 different mass spectrometers with the objective of assessing the reliability of untargeted metabolomics approaches in obtaining comparable metabolomics profiles. This was estimated by measuring the proportion of common spectral information extracted from the different LCMS and NMR platforms. Biological samples obtained from 2 different conditions were analysed by the partners using their own in-house protocols. Test #1 examined urine samples from adult volunteers either spiked or not spiked with 32 metabolite standards. Test #2 involved a low biological contrast situation comparing the plasma of rats fed a diet either supplemented or not with vitamin D. The spectral information from each instrument was assembled into separate statistical blocks. Correlations between blocks (e.g., instruments) were examined (RV coefficients) along with the structure of the common spectral information (common components and specific weights analysis). In addition, in Test #1, an outlier individual was blindly introduced, and its identification by the various platforms was evaluated. Despite large differences in the number of spectral features produced after post-processing and the heterogeneity of the analytical conditions and the data treatment, the spectral information both within (NMR and LCMS) and across methods (NMR vs. LCMS) was highly convergent (from 64 to 91 % on average). No effect of the LCMS instrumentation (TOF, QTOF, LTQ-Orbitrap) was noted. The outlier individual was best detected and characterised by LCMS instruments. In conclusion, untargeted metabolomics analyses report consistent information within and across instruments of various technologies, even without prior standardisation. [ABSTRACT FROM AUTHOR]

Camellianin A is a major active constituent of Adinandra nitida . A LC–MS/MS method for the determination of camellianin A and its metabolite (camellianin B) in rat plasma and tissues was developed and applied to a pharmacokinetics and tissue distribution study. Samples were separated on a Waters HSS T3 column with a mobile phase consisted of methanol and water (containing 0.1% formic acid). MS/MS detection was carried out on a triple-quadruple mass spectrometer under negative ESI mode. Pharmacokinetics study showed that camellianin A was rapidly eliminated with a t 1/2 of 92.6 ± 41.4 h and CL of 3.19 ± 0.471 L/min/kg. Additionally, camellianin A showed a low oral bioavailability of 2.99% and a narrow tissue distribution; however, camellianin B was proved to have a wide tissue distribution with brain penetration. The data presented in this study provides useful information for the further applications of A. nitida and camellianin A. [ABSTRACT FROM AUTHOR]

Zhi-Zi-Da-Huang decoction (ZZDHD), consisting of Gardenia jasminoides Ellis, Rheum palmatum L., Citrus aurantium L. and Sojae Semen Praeparatum, is a widely used traditional Chinese medicine preparation for the treatment of acute or chronic hepatic diseases. In the present study, a sensitive and selective ultra-high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (UHPLC–Q-TOF-MS) method was developed to separate and identify the absorbed components and metabolites in rat plasma after oral administration of ZZDHD. The plasma samples were pretreated by protein precipitation and separated on a Shim-pack XR-ODS C 18 column (75 mm × 3.0 mm, 2.2 μm) using a gradient elution program. Mass spectrometric detection was performed on an Agilent 6520 Q-TOF mass spectrometer equipped with electrospray ionization (ESI) source in positive and negative ion modes. By comparing the retention time, high resolution mass data of blank plasma and dosed plasma, a total of 43 constituents, including 21 prototype compounds and 22 metabolites were identified or tentatively characterized. Results indicated that glucuronidation and sulfation were the main metabolic pathways of iridoid glycosides and anthraquinones, glucuronidation was the main metabolic pathways of flavanone-related compounds. It is concluded the developed UHPLC–Q-TOF-MS method with high sensitivity and resolution is suitable for identifying and characterizing the absorbed components and metabolites of ZZDHD, and the results will provide essential data for further studying the relationship between the chemical components and pharmacological activity of ZZDHD. [ABSTRACT FROM AUTHOR]

A sensitive and versatile, ultra-high performance, liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method coupled to pre-column derivatization for the simultaneous determination of 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), dopamine (DA), norepinephrine (NE), homovanillic acid (HVA), γ-aminobutyric acid (GABA) and glutamic acid (Glu) was developed and validated in rat plasma. The analytes were dansylated under strong alkaline conditions after protein precipitation extraction, which were analyzed on a BEH C 18 column using a gradient elution. The lower limit of quantification (LLOQ) values for 5-HT, 5-HIAA, DA, NE, HVA, GABA and Glu were 1.00, 1.00, 0.991, 0.992, 1.02, 1000, and 5030 pmol/mL, respectively. Good linearity was obtained ( r > 0.99) and the intra- and inter-day precisions of the method (relative standard deviation, RSD%) were lower than 12%. The method was novel, sensitive and specific which can provide an alternative method for the quantification of neurotransmitters and their metabolites in plasma samples. [ABSTRACT FROM AUTHOR]

The metabolism of gentiopicroside in vivo was studied by LC/MS following 2,4-dinitrophenylhydrazine derivatization for the first time. The ionization efficiency of the major metabolites erythrocentaurin and gentiopicral were greatly enhanced by the new analytical method developed, and they were successfully detected in rat plasma after oral administration of gentiopicroside. Methyl 4-formylbenzoate was used as the internal standard to quantify erythrocentaurin and gentiopicral in rat plasma in negative mode by UPLC–TOF-MS. It was found that erythrocentaurin reached the maximum plasma concentration of 625.2 ± 246.3 ng/mL at about 2 h and gentiopicral reached the maximum plasma concentration of 157.6 ± 86.6 ng/mL at about 4 h after oral administration of gentiopicroside at a dose of 200 mg/kg. The metabolic pathway of gentiopicroside to erythrocentaurin and gentiopicral was proposed. The monoterpene compound gentiopicroside was found to be metabolized to dihydroisocoumarin in vivo which may be responsible for the pharmacological effect of gentiopicroside. The results may shed light on clinical efficacy of gentiopicroside and the new analytical method developed may assist in studies for the metabolism of other natural iridoids and secoiridoids in vivo . [ABSTRACT FROM AUTHOR]

Neuroactive metabolites in the kynurenine pathway of tryptophan catabolism are associated with neurodegenerative disorders. Tryptophan is transported across the blood–brain barrier and converted via the kynurenine pathway to N-formyl- l -kynurenine, which is further degraded to l -kynurenine. This metabolite can then generate a group of metabolites called kynurenines, most of which have neuroactive properties. The association of tryptophan catabolic pathway alterations with various central nervous system (CNS) pathologies has raised interest in analytical methods to accurately quantify kynurenines in body fluids. We here describe a rapid and sensitive reverse-phase HPLC–MS/MS method to quantify l -kynurenine (KYN), kynurenic acid (KYNA), 3-hydroxy- l -kynurenine (3HK) and anthranilic acid (AA) in rat plasma. Our goal was to quantify these metabolites in a single run; given their different physico-chemical properties, major efforts were devoted to develop a chromatography suitable for all metabolites that involves plasma protein precipitation with acetonitrile followed by chromatographic separation by C18 RP chromatography, detected by electrospray mass spectrometry. Quantitation range was 0.098–100 ng/ml for 3HK, 9.8–20,000 ng/ml for KYN, 0.49–1000 ng/ml for KYNA and AA. The method was linear ( r > 0.9963) and validation parameters were within acceptance range (calibration standards and QC accuracy within ±30%). [ABSTRACT FROM AUTHOR]

CAT ((+)-(13aS)-deoxytylophorinine) is a novel anticancer drug belonging to phenanthroindolizidine alkaloids. A sensitive and reliable liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for simultaneous quantification of CAT and its pharmacologically active 3-O-desmethyl metabolite (S-4) was developed and validated in rat plasma using rotundine as the internal standard (IS). CAT, S-4 and IS were extracted by acetonitrile protein precipitation and separated on an Eclipse XDB-C18 column (1.8 μm, 4.6 mm × 50 mm) with acetonitrile–water (27:73, v/v) mobile phase containing 0.1% formic acid at a 0.4 mL/min flow rate. Positive ion electrospray ionization in multiple reaction monitoring mode was employed to measure CAT, S-4 and IS by monitoring the transitions m/z 364.2 → 70.1 for CAT, 350.1 → 70.1 for S-4 and 356.2 → 192.2 for IS. Good linear correlation ( r 2 > 0.991) was achieved for CAT and S-4 over the range of 0.214–128.16 and 0.044–11.00 ng/mL, respectively. The lower limit of quantification was 0.214 ng/mL for CAT and 0.044 ng/mL for S-4, using 50 μL rat plasma samples. The intra- and inter-day precisions were not exceed 15% and the accuracy ranged between 94.80% and 108.22%. The average extraction recoveries of both analytes were greater than 94.62%. The method was successfully applied to the pharmacokinetic study of CAT and S-4 in rats after oral administration. [ABSTRACT FROM AUTHOR]

Efficacy assessments using a combination of ibrutinib and lenalidomide necessitate the development of an analytical method for determination of both drugs in plasma with precision. A high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed for the simultaneous determination of lenalidomide, ibrutinib, and its active metabolite PCI45227 in rat plasma. Extraction of lenalidomide, ibrutinib, PCI45227 and tolbutamide (internal standard; IS) from 50 μl rat plasma was carried out by liquid–liquid extraction with ethyl acetate:dichloromethane (90:10) ratio. Chromatographic separation of analytes was performed on YMC pack ODS AM (150 mm × 4.6 mm, 5 μm) column under gradient conditions with acetonitrile:0.1% formic acid buffer as the mobile phases at a flow rate of 1 ml/min. Precursor ion and product ion transition for analytes and IS were monitored on a triple quadrupole mass spectrometer, operated in the selective reaction monitoring with positive ionization mode. Method was validated over a concentration range of 0.72–183.20 ng/ml for ibrutinib, 0.76–194.33 ng/ml for PCI-45227 and 1.87–479.16 ng/ml for lenalidomide. Mean extraction recovery for ibrutinib, PCI-45227, lenalidomide and IS of 75.2%, 84.5%, 97.3% and 92.3% were consistent across low, medium, and high QC levels. Precision and accuracy at low, medium and high quality control levels were less than 15% across analytes. Bench top, wet, freeze–thaw and long term stability was evaluated for all the analytes. The analytical method was applied to support a pharmacokinetic study of simultaneous estimation of lenalidomide, ibrutinib, and its active metabolite PCI-45227 in Wistar rat. Assay reproducibility was demonstrated by re-analysis of 18 incurred samples. [ABSTRACT FROM AUTHOR]

Isobavachalcone (IBC) is a prenylated chalcone and belongs to the class of flavonoids, which is an active component isolated from Psoralea corylifolia L. IBC showed a range of significant pharmacological activities, including antibacterial, anticancer, anti-reverse transcriptase and antioxidant actions. In this research, the mass spectral fragmentation pattern of IBC was investigated to predict the in vivo metabolites, and five phase I metabolites and ten phase II metabolites of IBC in rat bile were elucidated and identified after oral administration using novel LC–ESI-MS n and LC–NMR method. The molecular structures of these metabolites were proposed on the basis of the characteristics of their precursor ions, product ions, MS/MS fragment behaviors and chromatographic retention time. The phase I metabolites were mainly biotransformed via the hydroxylation, reduction, cyclization and oxidative cleavage reactions. The phase II metabolites were mainly identified as the glucuronide conjugates and sulfated conjugates. All these findings were reported for the first time and would contribute to a further understanding of the in vivo intermediate processes and metabolic mechanism of isobavachalcone and its analogs. [ABSTRACT FROM AUTHOR]

Acetaminophen is known to cause hepatoxicityvia the formationof a reactive metabolite, N-acetyl p-benzoquinone imine (NAPQI), as a result of covalent binding to liverproteins. Serum albumin (SA) is known to be covalently modified byNAPQI and is present at high concentrations in the bloodstream andis therefore a potential biomarker to assess the levels of proteinmodification by NAPQI. A newly developed method for the absolute quantitationof serum albumin containing NAPQI covalently bound to its active sitecysteine (Cys34) is described. This optimized assay represents thefirst absolute quantitation of a modified protein, with very low stoichiometricabundance, using a protein-level standard combined with isotope dilution.The LC–MS/MS assay is based on a protein standard modifiedwith a custom-designed reagent, yielding a surrogate peptide (followingdigestion) that is a positional isomer to the target peptide modifiedby NAPQI. To illustrate the potential of this approach, the methodwas applied to quantify NAPQI-modified SA in plasma from rats dosedwith acetaminophen. The resulting method is highly sensitive (capableof quantifying down to 0.0006% of total RSA in its NAPQI-modifiedform) and yields excellent precision and accuracy statistics. A time-coursepharmacokinetic study was performed to test the usefulness of thismethod for following acetaminophen-induced covalent binding at fourdosing levels (75–600 mg/kg IP), showing the viability of thisapproach to directly monitor in vivosamples. Thisapproach can reliably quantify NAPQI-modified albumin, allowing directmonitoring of acetaminophen-related covalent binding. [ABSTRACT FROM AUTHOR]

Glycycoumarin is a major bioactive coumarin of licorice (Glycyrrhiza uralensis), one of the most popular herbal medicines worldwide. In this work, the metabolism of glycycoumarin in rats was investigated. After oral administration of 40 mg/kg glycycoumarin, 4 and 10 metabolites were respectively detected in rats plasma and urine samples by liquid chromatography coupled with mass spectrometry (LC/MS). These metabolites were tentatively characterized by analyzing their tandem mass spectra and high-resolution mass spectra, and the structures of glucuronides were confirmed by β-glucuronidase hydrolysis. Glycycoumarin mainly undertakes hydroxylation and glucuronidation metabolism, accompanied by hydrogenation and dehydrogenation as minor reactions. Two hydroxylated metabolites, 4''-hydroxyl glycycoumarin and 5''-hydroxyl glycycoumarin, were obtained by microbial transformation of Syncephalastrum racemosum AS 3.264, and their structures were fully identified by 1D and 2D NMR. Both metabolites are new compounds. Furthermore, they were proved to be catalyzed by P450 enzymes by rat liver microsomes incubation experiments. Finally, a metabolic pathway of glycycoumarin in rats was proposed. This is the first systematic study on metabolites identification of glycycoumarin. [ABSTRACT FROM AUTHOR]

Highlights: [•] Arachidonic acid (AA) is metabolized by cytochrome P450 enzymes to biologically active metabolites. [•] P450-mediated metabolites of AA are mostly present in tissues as bound to phospholipids. [•] A validated assay is developed to quantitate free concentrations of AA metabolites in the liver. [•] The assay is applied to study the effects of hepatic ischemia on the metabolites. [•] Hepatic ischemia increased the free concentrations of AA and most of its metabolites in the liver. [ABSTRACT FROM AUTHOR]

Highlights: [•] Development of a LC/MS/MS method for the analysis of MC-LR and its GSH metabolites in rat liver. [•] Pretreatment conditions were optimized to extract analytes efficiently. [•] Combined use of SPE columns increases analyte purity when isolated from a complex matrix. [•] This method has been validated with excellent results. [•] Time- and dosage-effect studies were conducted using rat liver. [ABSTRACT FROM AUTHOR]

Highlights: [•] A practical approach for metabolism of chiral drugs was based on combined LC/MS/MS. [•] Racemic tetrahydropalmatine was chosen as the model chiral drug. [•] UPLC-QTOF/MS was used to identify the metabolites of THP enantiomers in rat urine. [•] LC-QqQ/MS was applied for quantification of THP enantiomers and their metabolites. [•] Semi-quantification of three phase I and two phase II metabolites was performed. [Copyright &y& Elsevier]

Highlights: [•] First UPLC/MS/MS method for simultaneous detection of arctigenin and metabolites. [•] High absorption permeability of arctigenin demonstrated in both cell and rat model. [•] Extensive intestinal first-pass metabolism of arctigenin identified in rats. [Copyright &y& Elsevier]

Highlights: [•] Forty-two metabolites of honokiol were tentatively identified in rat feces, twenty-six of which were first reported. [•] Two novel classes of metabolites, methylated and dimeric metabolites of honokiol, were identified in vivo for the first time. [•] Systemic understanding of the metabolic pathways of honokiol in rat feces, urine and plasma. [ABSTRACT FROM AUTHOR]

Abstract: Metabolic profiles of prodrug fosinopril and pharmacologically active metabolite fosinoprilat were studied using human or rat liver microsomes and S9 fractions. Metabolites were identified by ultra high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS) using electrospray ionization in the positive and negative ion mode. They were characterized by accurate MS and MS/MS spectra and based on their different fragmentation pathways. With human liver microsomes fosinopril was metabolized via hydroxylation, glucuronidation, and hydrolysis to fosinoprilat. As expected the main metabolite was fosinoprilat and it was further hydroxylated and glucuronidated. However, these metabolites were not detected after incubation of fosinoprilat with human liver microsomes, indicating that metabolic reactions occur in sequence and fosinopril is hydrolyzed after glucuronidation or hydroxylation. With the developed UHPLC/Q-TOF-MS method once or twice hydroxylated fosinopril metabolites were detected for the first time and different regioisomers were separated. It was observed that the hydrolysis of fosinopril to fosinoprilat was more efficient with rat than with human liver microsomes, and therefore more hydroxylated fosinoprilat metabolites were detected when rat liver microsomes were used. Glucuronidation of fosinopril was not observed with rat liver microsomes. [Copyright &y& Elsevier]

Dimethocaine (DMC, larocaine), a synthetic derivative of cocaine, is a widely distributed 'legal high' consumed as a 'new psychoactive substance' (NPS) without any safety testing, for example studies of metabolism. Therefore, the purpose of this work was to study its in-vivo and in-vitro metabolism by use of liquid chromatography-(high resolution) mass spectrometry (LC-HRMS). DMC was administered to male Wistar rats (20 mg kg) and their urine was extracted either by solid-phase extraction after enzymatic cleavage of conjugates or by use of protein precipitation (PP). The metabolites were separated and identified by LC-HRMS. The main phase I reactions were ester hydrolysis, deethylation, hydroxylation of the aromatic system, and a combination of these. The main phase II reaction was N-acetylation of the p-aminobenzoic acid part of the unchanged parent compound and of several phase I metabolites. The metabolites identified were then used for identification of DMC in rat urine after application of a common user's dose. By use of GC-MS and LC-MS standard urine-screening approaches (SUSAs), DMC and its metabolites could be detected in the urine samples. [ABSTRACT FROM AUTHOR]

Highlights: [•] An LC–MS/MS method for the relative determination of five metabolites in rat urine. [•] The relative quantification strategy for the pharmacokinetic research of metabolites of drugs. [•] A strategy to study the mechanism of Traditional Chinese Medicine formula by metabolite research. [ABSTRACT FROM AUTHOR]

Highlights: [•] A LC–MS/MS method was developed and validated. [•] Dip was extensively metabolized to three metabolites. [•] LC–MS/MS was applied to determine the pharmacokinetic of Dip and its metabolites. [Copyright &y& Elsevier]

Highlights: [•] It is the first report for bioavailability study of larotaxel in rats. [•] It is the first method for determination of larotaxel and its metabolites. [•] A simple and rapid LC–MS/MS method was developed and validated. [Copyright &y& Elsevier]

Highlights: [•] Imperatorin and its metabolite xanthotoxol in plasma were analyzed by LC–MS. [•] HF-LPME was employed to prepare plasma samples. [•] A comparison between HF-LPME and deproteinization with methanol was operated. [Copyright &y& Elsevier]

Highlights: [•] Evaluate the pharmacokinetic profiles of sophoricoside and its metabolite. [•] Excretion studies of sophoricoside and its metabolite in bile, urine and feces. [•] Assay of sophoricoside and its metabolite after oral administration of sophoricoside. [•] Determination of sophoricoside and its metabolite genistein by LC–MS. [•] There were double peaks of genistein in rat plasma. [Copyright &y& Elsevier]

Highlights: [•] Nine phase I and four phase metabolites of lapachol were identified in rats by LC-ESI–MS n . [•] This work gave us a new insight into the metabolic pathways of lapachol in vivo. [•] More information about the cleavage rules of these metabolites were collected and proposed. [Copyright &y& Elsevier]

A new ultra-performance liquid chromatography–electrospray ionization mass spectrometry (UPLC–MS/ESI) method for simultaneous determination of venlafaxine (VEN) and its metabolite O-desmethylvenlafaxine (ODV) in rat plasma has been developed and validated using Venlafaxine d6 as the internal standard. The compounds and internal standard were extracted from plasma by solid phase extraction. The UPLC separation of the analytes was performed on ACQUITY UPLC® BEH Shield RP18 (1.7µm, 100mm×2.1mm) column, using isocratic elution with mobile phase constituted of water (containing 2mM ammonium acetate): acetonitrile (20:80, v/v) at a flow rate of 0.3mL/min. All of the analytes were eluted within 1.5min. The compounds were ionized in the electrospray ionization (ESI) ion source of the mass spectrometer, operating in multiple reaction monitoring (MRM) and positive ion mode. The precursor to product ion transitions monitored for VEN, ODV and Venlafaxine d6 were m/z 278.3→121.08, 264.2→107.1 and 284.4→121.0, respectively. The developed and validated method was used for the pharmacokinetic study of VEN in rats. [ABSTRACT FROM AUTHOR]

Highlights: [•] A LC–MS/MS method was developed and validated for determination of flavonoids. [•] The lower limits of quantitations of six flavonoids were lower than 1ngmL−1. [•] The main pharmacokinetic parameters of flavonoids of mulberry leaves were reported. [•] It is the first pharmacokinetic study of astragalin. [Copyright &y& Elsevier]

Highlights: [•] We develop a method for the determination of trantinterol and its metabolites for the first time. [•] The method has short analysis time, good sensitivity and selectivity. [•] We report the excretion of trantinterol and its four metabolites in rats for the first time. [ABSTRACT FROM AUTHOR]